8504
E. Petricci et al. / Tetrahedron Letters 48 (2007) 8501–8504
H.; Jackstell, R.; Beller, M. Tetrahedron Lett. 2005, 46,
7401–7404; Seayad, A. M.; Selvakumar, K.; Ahmed, M.;
Beller, M. Tetrahedron Lett. 2003, 44, 1679–1982; Seayad,
A.; Ahmed, M.; Klein, H.; Jackstell, R.; Gross, T.; Beller,
M. Science 2002, 297, 1676–1679.
MW, H2, (100 psi)
Pd(OH)2/C
Bn
Bn
MeOH, 100 °C, 20 min
N
BnOOC
N
X
X
13 X = O
7. Breit, B. Tetrahedron Lett. 1998, 39, 5163–5166.
8. Petricci, E.; Mann, A.; Schoenfelder, A.; Rota, A.; Taddei,
M. Org. Lett. 2006, 8, 3725–3728.
9. Xantphos: 9,9-dimethyl-4,5-bis(diphenylphosphine)xan-
thene (a) Kranenburg, M.; van der Burgt, Y. E. M.;
Kamer, P. C. J.; van Leeuwen, P. W. N. M. Organomet-
allics 1995, 14, 3081–3089; The ligand is commercially
available from Sigma–Aldrich, Stream and other chemical
suppliers; (b) Garbacia, S.; Desai, B.; Lavastre, O.; Kappe,
C. O. Org. Lett. 2003, 68, 9136–9139.
19 X = NMe
NH2
HOOC
N
24 X = O 90%
25 X = NMe 87%
Scheme 5. MW assisted hydrogenolysis.
10. Other attempts under conventional conditions were found
to stop at the stage of the imine: (a) Baig, T.; Kalck, P.
Chem. Commun. 1992, 1373–1375; (b) Baig, T.; Molinier,
J.; Kalck, J. J. Organomet. Chem. 1993, 455, 219–226.
11. All reactions were carried out inside the cavity of a
Discover microwave oven for organic synthesis, produced
by CEM Corporation.
In conclusion, we have demonstrated that hydro-
aminomethylation of alkenes can be carried out in short
time with a commercially available MW apparatus and
that hydrogenolysis of benzylamines and benzyl esters
can be accelerated under MW irradiation. Several new
substituted a-amino acids were obtained from allylgly-
cine using this approach.
12. Collier, P. N.; Patel, I.; Taylor, R. J. K. Tetrahedron Lett.
2002, 43, 3401–3404; Namba, K.; Shinada, T.; Teramoto,
T.; Ohfune, Y. J. Am. Chem. Soc. 2000, 122, 10708–10709;
Collier, P. N.; Campbell, A. D.; Patel, I.; Taylor, R. J. K.
Tetrahedron Lett. 2000, 41, 7115–7118; Girard, A.; Greck,
C.; Genet, J. P. Tetrahedron Lett. 1998, 39, 4259–4262;
Ojima, I.; Tzamarioudaki, M.; Eguchi, M. J. Org. Chem.
1995, 60, 7078–7079; Kitagawa, O.; Hanano, T. I.; Kikuchi,
N.; Taguchi, T. Tetrahedron Lett. 1993, 34, 2165–2168.
13. (a) Nolen, E. G.; Kurish, A. J.; Potter, J. M.; Donahue, L.
A.; Orlando, M. D. Org. Lett. 2005, 7, 3383–3386; (b)
Chowdhury, A. R.; Boons, G.-J. Tetrahedron Lett. 2005,
46, 1675–1678; (c) Busscher, G. F.; Rutjes, F. P. J. T.; Van
Delft, F. L. Tetrahedron Lett. 2004, 45, 3629–3632; (d)
McGarvey, G. J.; Benedum, T. E.; Schmidtmann, F. W.
Org. Lett. 2002, 4, 3591–3594; (e) Randl, S.; Gessler, S.;
Wakamatsu, H.; Blechert, S. Synlett 2001, 430–432; (f)
O’Leary, D. J.; Miller, S. J.; Grubbs, R. H. Tetrahedron
Lett. 1998, 39, 1689–1692.
14. Rodriquez, M.; Bruno, I.; Cini, E.; Marchetti, M.; Taddei,
M.; Gomez-Paloma, L. J. Org. Chem. 2006, 71, 103–107.
15. Biphephos: {[3,30-di-tert-Butyl-20-(diphenoxymethoxy)-5,
50-dimethoxybiphenyl-2-yl]oxy}dibenzo[d,f][1,3]dioxepine.
(a) Billig, E.; Abatjoglou, A. G.; Bryant, D. R. U.S. Patent
4,668,651, 1987 and U.S. Patent 4,769,498, 1988; (b)
Cuny, G. D.; Buchwald, S. L. J. Am. Chem. Soc. 1993,
115, 2066–2067.
16. In a typical experiment, a secondary amine (1 mmol) and
allylglycine 12 (1 mmol) were dissolved in dry EtOH
(2 mL). (PPh3)3Rh(CO)H (18 mg, 0.02 mmol) and Biphe-
phos (63 mg, 0.08 mmol) were added. The yellow solution
obtained was submitted to pressurized syngas at 90 psi
(6 atm) and heated for 30 min at 110 °C by microwave
irradiation at 150 W (value previously settled on the
microwave oven). The flask was cooled and the internal
gas released. The reaction mixture was evaporated in
vacuo and the yellow oil obtained was purified by flash
chromatography.
17. To our knowledge, this is the first example of MW assisted
hydrogenolysis in the presence of H2 gas. For MW assisted
transfer hydrogenolysis see: (a) Quai, M.; Barbaglia, W.;
Cereda, E. Tetrahedron Lett. 2007, 48, 1241–1244; (b)
Leijondahl, K.; Fransson, A. B. L.; Backvall, J. E. J. Org.
Chem. 2006, 71, 8622–8625; (c) Srinivasa, G. R.; Babu, S.
N. N.; Lakshmi, C.; Gowda, D. C. Synth. Commun. 2004,
34, 1831–1836; (d) Daga, M. C.; Taddei, M.; Varchi, G.
Tetrahedron Lett. 2001, 42, 5191–5194.
Acknowledgements
This work was carried out with the financial support of
MUR (Rome) as project PRIN-2005. The University of
Siena is also acknowledged for funding (PAR project
2006).
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